As one form of fuel cell systems, there has been known one which is described in Patent Document 1. As shown in FIG. 1 of Patent Document 1, in the fuel cell system 1, when a power supply to the fuel cell system 1 is recovered, the operation step is moved directly to a predetermined stopping stage which corresponds to respective steps right before the power supply to the fuel cell system 1 was discontinued, and that the fuel cell system 1 is then stopped through predetermined stopping steps subsequent thereto. Thus, it can be avoided that the main body of a fuel cell 20 and a reforming apparatus 10 are damaged due to deterioration of a catalyzer or the like.